MPX2003

– UP TO 140kHz ALL-IN-ONE FLYBACK CONTROLLER

MPX2003 Rev. 1.0

MonolithicPower.com

25

8/5/2022

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© 2022 MPS. All Rights Reserved.

Secondary Over-Voltage Protection (SOVP)

If the FB voltage exceeds the OVP threshold

(VOVP) and lasts longer than the OVP delay time

(tOVP-D), the secondary over-voltage protection

(SOVP) flag is set to high and switching stops.

Switching reverts to normal modulation once the

FB voltage returns to VREF. During SOVP, there

is an extra current (IBLD) drawn from the VDD pin.

This

current

helps

ease

the

over-voltage

condition by discharging the VDD capacitor.

FB Open-Loop Protection (FBOLP)

If there are fault conditions (i.e. FB shorted to

SGND or an upper FB resistor is open), the

MPX2003 loses its feedback loop and VOUT goes

out of regulation. To protect the circuit from being

further damaged, the MPX2003 implements a

cross check between VOUT and the FB voltage.

If VDD exceeds VDD-RDY, this means that VDD is no

longer supplied by SRD. If the FB voltage is still

below VFBO, the secondary IC initiates FB open-

loop protection (FBOLP) after a validation time

(tFBO).

The internal leakage current (IFB) guarantees

that the FB voltage is always pulled to SGND

when the FB pin is open.

SR Gate Open/Short Protection

(SGOP/SGSP)

If SDRV is set but the SRD voltage remains low

during the conduction period, this indicates that

the SR may not be successfully turned on due to

an unexpected fault condition, such as an open

gate or a broken MOSFET. The MPX2003

implements SR gate open protection (SGOP) to

protect the circuitry from being further damaged

under these conditions.

The threshold for SR driver open detection is

VSGO, and the condition must remain for 8

consecutive switching cycles for validation. If

SGOP is triggered, the secondary IC does not

recover until there is another primary IC self

start-up.

If SDRV detects that the connected resistor is

below 1kΩ once VDD reaches VDD-ON, this means

that SDRV is shorted to SGND. Switching stops

until the primary IC starts up again.

SRD Abnormal Protection (SRDP)

If the power supply of the secondary IC is

successfully set up and there are 17 consecutive

primary switching pulses but the SR gate is not

triggered by SRD detection, SRD abnormal

protection (SRDP) is triggered. Switching stays

off and COMP is pulled to ground. The

secondary IC does not recover until the

secondary IC or primary IC trigger UVLO. Then

the secondary IC starts switching once a valid

signal is detected on SRD.

Secondary Over-Temperature Protection

(SOTP)

To prevent any thermal damage on the chip,

secondary over-temperature protection (SOTP)

sets

the SOTP

flag

high

if

the

junction

temperature exceeds TOTP-S. The protection flag

is latched until the junction temperature drops by

TΔ-S.